MIDI keyboards

From the ALSA wiki

A MIDI keyboard is a piano keyboard with special electronics for sending
and receiving MIDI files. Recent MIDI keyboards have a
sound quality as good as or better than mid-price grand pianos and
upright pianos. Recent MIDI keyboards also have a weighted key mechanism
which feels truly identical to the keys of a grand piano.

If you are considering which musical instrument to buy for making music,
a MIDI keyboard is an excellent choice because

MIDI keyboards do not ever need to be tuned, thus saving the cost of
regular piano tuning.

MIDI keyboards have a volume control and can be used with
headphones. This is very useful if you do not want to disturb other
people.

MIDI keyboards are much more portable than ordinary pianos, weighing
only about 70kg/150lbs and being about the same size as an upright
piano.

MIDI keyboards can play music automatically like a virtual virtuoso
accompanist.

There are many different makes of MIDI keyboard: Yamaha, Roland,
Korg, etc. It is best to get a MIDI keyboard with "weighted keys"
that move and feel like real piano keys. The price range is USD
1000-3000. I personally prefer Yamaha Clavinovas and think the
Yamaha CLP-170 Clavinova (at time of writing this in 2004) is equal
in sound quality and touch to any mid-price grand piano -- a really
excellent musical instrument!